Acoustic Wave Device Suppressing Spurious Wave in Lamb Wave and Filter Including the Same

The present invention relates to an acoustic wave device for suppressing spurious waves in Lamb waves and a filter including the same, and more specifically, to an acoustic wave device capable of suppressing spurious wave components propagating along a piezoelectric substrate by forming a cavity within a support substrate in contact with the piezoelectric substrate, and a filter including such a device.

In wireless communication devices, resonators and filters utilizing surface acoustic waves (SAW) and bulk acoustic waves (BAW) have been widely used. However, with the advent of 5G standards and subsequent wireless communication standards that utilize high-frequency bands above 2.7 GHz, there is a growing demand for resonators capable of handling high frequencies, wide bandwidths, and high power.

In particular, Patent Document 1 proposes an acoustic wave resonator that employs Lamb waves, which are a type of plate wave, to enhance frequency characteristics toward higher frequencies.

However, in the device disclosed in Patent Document 1, degradation of device performance occurs due to spurious waves generated in the Lamb wave, and thus a technical solution to address this issue is required.

The technical problem to be solved by the present invention is to provide a resonator having a cavity configured to sufficiently suppress spurious waves generated in an acoustic wave device using Lamb waves, and a filter including the same.

The technical problems of the present invention are not limited to those mentioned above, and other technical problems not explicitly stated will be clearly understood by those skilled in the art from the description below.

To solve the aforementioned technical problems, an acoustic wave device for suppressing spurious waves in a Lamb wave according to an embodiment of the present invention includes: a support substrate; a piezoelectric substrate supported by the support substrate and defining a first resonator region on the support substrate; and a first resonator and a second resonator, which are disposed in the first resonator region of the piezoelectric substrate, each including a plurality of interdigital transducer (IDT) electrodes and electrically connected to each other. The support substrate includes a first cavity formed beneath the first resonator and a second cavity formed beneath the second resonator, wherein the first and second cavities are interconnected within the support substrate.

In some embodiments of the present invention, the piezoelectric substrate further defines a second resonator region, and a third resonator comprising a plurality of IDT electrodes is further included in the second resonator region. The support substrate further includes a third cavity formed beneath the third resonator, and the first cavity and the third cavity are not connected to each other. The first or second resonator and the third resonator may propagate Lamb waves in mutually different frequency bands.

In some embodiments of the present invention, the support substrate may include a partition wall that separates the first cavity from the third cavity.

In some embodiments of the present invention, each of the first to third resonators includes a bus bar, and the partition wall may be disposed to overlap, in a depth direction of the support substrate, with at least one of the bus bars of the first to third resonators.

In another embodiment of the present invention for solving the above-described technical problem, an acoustic wave device for suppressing spurious waves in Lamb waves includes: a support substrate; a piezoelectric substrate supported by the support substrate and having a first resonator region defined thereon; and a first resonator and a second resonator, each including a plurality of interdigital transducer (IDT) electrodes, disposed in the first resonator region of the piezoelectric substrate.

The support substrate includes a first cavity formed beneath the first resonator and a second cavity formed beneath the second resonator.

The first cavity and the second cavity are not connected to each other, and the Lamb waves propagated by the first and second resonators have mutually different frequency bands.

In some embodiments of the present invention, the support substrate may include a partition wall formed between the first cavity and the second cavity.

In some embodiments of the present invention, the first and second resonators may each include a bus bar, and the partition wall may be arranged to overlap, in the depth direction of the support substrate, with at least one of the bus bars of the first and second resonators.

Other specific details of the embodiments are included in the detailed description and drawings.

The acoustic wave device for suppressing spurious waves in Lamb waves according to the present invention can effectively suppress spurious waves of Lamb waves by allowing resonators that propagate Lamb waves in the same frequency band to share a cavity formed beneath them.

The effects of the present invention are not limited to those mentioned above, and other effects not explicitly stated can be clearly understood by those skilled in the art from the entirety of this specification.

The advantages and features of the present invention and the method for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. These embodiments are provided only to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the present invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

“And/or” includes each of the mentioned items and all combinations of one or more of the mentioned items.

The terms used in this specification are to describe the embodiments and are not to limit the present invention. In this specification, singular forms also include plural forms unless specially stated otherwise in the phrases. The terms “comprises” and/or “comprising” used in this specification means that the mentioned components, steps, operations, and/or elements do not exclude the presence or addition of one or more other components, steps, operations and/or elements.

In addition, throughout the specification, when a part is said to be "connected" to another part, this also includes "indirectly" or "electrically connected" cases with intervention of other members or components therebetween, as well as "directly connected" cases.

In addition, throughout the specification, the description that each layer (film), region, pattern, or structure is formed "above/on" or "beneath/under" a substrate, each layer (film), region, pad, or pattern includes both cases that they are formed directly and formed with intervention of other layers. The criteria for being above/on or beneath/under each layer are explained with reference to the drawings.

In addition, expressions such as 'first, second', and the like are only used to distinguish a plurality of components, and do not limit the sequence of the components or other features.

In addition, the flowcharts shown in the drawings merely illustrate an exemplary sequence for achieving the most desirable results in implementing the present invention. It is understood that additional steps may be added or certain steps may be omitted as necessary.

Unless defined otherwise, all the terms (including technical and scientific terms) used in this specification may be used as meanings that can be commonly understood by those skilled in the art. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless clearly and specifically defined.

1 FIG. 2 FIG. 1 FIG. 3 FIG. 1 FIG. is a plan view illustrating an acoustic wave device for suppressing spurious waves in Lamb waves according to an embodiment of the present invention.is a cross-sectional view taken along line A–A′ of, andis a cross-sectional view taken along line B–B′ of.

1 3 FIGS.through 100 110 120 130 140 150 Referring to, the acoustic wave deviceaccording to an embodiment of the present invention may include a support substrate, a piezoelectric substrate, interdigital transducer (IDT) electrodes, pads, bumps, and the like.

110 120 110 120 110 160 220 110 160 220 130 170 210 The support substratemay support the piezoelectric substrate, which has a relatively small thickness. The thickness of the support substratemay be greater than that of the piezoelectric substrate. The support substratemay include a first cavityand a second cavity, formed by removing portions of the support substrate. The first cavityand the second cavitymay attenuate the acoustic waves generated by the resonators,,.

2 3 FIGS.and 160 220 120 160 220 110 160 220 120 110 As partially shown in, the upper surfaces of the first cavityand the second cavityare defined by the lower surface of the piezoelectric substrate, and the side and bottom surfaces of the cavitiesandmay be defined by the side surfaces of the remaining support substrateafter partial removal. Accordingly, the first cavityand the second cavitymay each have a sealed structure defined by the lower surface of the piezoelectric substrateand the inner surfaces of the support substrate.

114 115 110 114 115 110 160 220 120 At least one partition wall,may be formed inside the support substrate. The partition walls,are portions of the support substratethat remain after forming the first cavityor the second cavity, and may contact and support the piezoelectric substrate.

114 115 110 130 170 130 170 114 115 130 170 120 Meanwhile, the partition walls,may partially overlap, in the depth direction of the support substrate, with the bus bars that are components of the resonators,. Through this configuration, the partition walls can serve a heat dissipation function by conducting heat generated during the operation of the resonators,. That is, the partition walls,are elongated in the longitudinal direction of the resonators,not only to support the piezoelectric substrate, but also to increase the contact area with the resonators for effective heat dissipation.

110 110 110 The support substratemay include, for example, a semiconductor material such as polycrystalline silicon or amorphous silicon. In another embodiment, the support substratemay be composed of a multilayer film. When the support substrateis formed as a multilayer structure, it may include a configuration of a silicon substrate, a silicon oxide layer, and a silicon nitride layer sequentially formed on the silicon substrate.

120 110 130 120 The piezoelectric substratemay be disposed on the support substrateand may propagate a Lamb wave, which is a type of plate wave that reflects and travels between the upper and lower surfaces in a region where the IDT electrodesare formed. The piezoelectric substratemay include, for example, materials such as LiTaO₃ (LT) or LiNbO₃ (LN).

10 20 30 120 10 20 30 120 120 A plurality of resonator regions,, andmay be defined on the piezoelectric substrate. Each of the resonator regions,, anddefined on the piezoelectric substratemay be distinguished as a region where an independent cavity is formed below the piezoelectric substrate.

160 10 220 20 160 220 115 110 10 160 20 220 A first cavitymay be formed beneath the first resonator region, and a second cavitymay be formed beneath the second resonator region. In this case, the first cavityand the second cavitymay be unconnected to each other. The description that "one cavity is unconnected to another" means that the two cavities are separated by a partition wallthat forms part of the support substrate. Furthermore, as will be described later, this may indicate that the Lamb waves propagating through the first resonator regionabove the first cavityand the Lamb waves propagating through the second resonator regionabove the second cavityexhibit different characteristics.

130 170 210 120 130 170 210 130 170 10 120 210 20 130 170 210 Resonators,,may be disposed on the piezoelectric substrate. The resonators,,may be distinguished a first resonatorand a second resonatordisposed on the first resonator regionof the piezoelectric substrate, and a third resonatordisposed on the second resonator region. Each of the resonators,,may include bus bars formed in parallel along the longitudinal direction, and interdigital transducer (IDT) electrodes alternately extending from the bus bars.

130 210 130 210 In some embodiments of the present invention, the first resonatorand the third resonatormay propagate Lamb waves having different characteristics. For example, the first resonatorand the third resonatormay propagate Lamb waves in different frequency bands.

130 170 10 In contrast, the first resonatorand the second resonator, which are disposed within the same first resonator region, may propagate Lamb waves in the same frequency band.

100 130 170 10 160 130 170 130 210 10 20 160 220 As such, in the acoustic wave deviceaccording to the embodiment of the present invention, the placement of resonators,that propagate Lamb waves in the same frequency band on the same first resonator regionabove the first cavityis intended to suppress spurious Lamb waves generated by the first resonatorand the second resonator. Meanwhile, resonators,that propagate Lamb waves in different frequency bands may be distinguished from each other by being disposed on the first resonator regionand the second resonator region, which are located respectively above different cavities—the first cavityand the second cavity.

Although embodiments of the present invention have been described so far with reference to the accompanying drawings, it will be apparent to those skilled in the art that the present invention may be performed in other forms without departing from the technical spirit or essential characteristics of the present invention. Therefore, the above-described embodiments should be understood as exemplary in all respects and are not limited.